I got rid of my old Nintendo 64 many years ago, but lately I've been feeling nostalgic for some of those old games (Borderlands 2 cannot hold a candle to Mario Kart 64). I've heard that emulators can play these games on a PC. How do I set that up?

Technologically, you and your 1990s nostalgia are in luck. Legally, you might be in a bit of a gray area. The emulator you've heard about is a combination of two types of software: The first is a program that plays the part of a virtual video-game console and the second is a ROM (read-only memory) file that replicates the game cartridge. Emulators exist for almost every ancient gaming platform you can imagine, from the Atari 2600 to the PlayStation 2. To satisfy your Nintendo 64 craving, check out Project64 for Windows or Sixtyforce for Mac OS X. Both work with keyboards, or you can use original Nintendo 64 controllers, which plug in to your computer with simple USB adapters (look for both controllers and adapters on Amazon and eBay).

Like emulators, ROMs are a snap to find on the Web; just search the name of any game and you'll likely find dozens of download sources. But also like emulators, they are legally dubious. Video-game manufacturers argue that emulators and ROMs infringe on copyrights, while computer gamers say they're fine to use under fair-use laws. A ROM user could argue that his computerized version is just a legal backup of a game he already owns in cartridge form, or that what he's doing is simple content shiftingwhat you do when you transfer a video from your computer to your tablet. "If a user does not own the original game, he's gambling that he will not get sued," says Derek Bambauer, a professor of intellectual property and Internet law at Brooklyn Law School, so content shifting is the best argument for legal use of ROMs. Adam Dachis, a senior writer at Lifehacker, agrees: "If you own the game and either can't play it on a system or don't want to use the system, I consider that a reasonable use."